John Langston (c. 1758 – 18 February 1812) was an English merchant banker and politician. He sat in the House of Commons of Great Britain and its successor the House of Commons of the United Kingdom for most of the years between 1784 and 1807.
Langston was the oldest son of James Haughton Langston and his wife Sarah, of Sarsden House in Oxfordshire.
In 1784 he married Sarah Goddard, daughter of John Goddard of Woodford Hall, Essex. They had one son (James Haughton Langston) and four daughters.
Langston was probably educated at Eton. He had a generous inheritance from his father, who died in 1795. As well as being a wine merchant in London, James Langston was a deputy governor of the Bank of England and founder of the merchant bank of Langston, Towgood and Amory. John inherited a partnership in the bank, shares in the British East India Company, the Sarsden and Churchill estates in Oxfordshire, and £300,000 (equivalent to £28 million in 2017).
Langston was a director of the Sun Fire Office from 1794 until his death. He aimed to buy himself a place in Parliament, but never found a safe seat. At the 1784 election he was returned after a contest as a Member of Parliament (MP) for Sudbury, an open borough with a reputation for venality where the government backed his candidacy.
At the next election, in 1790, he contested Bridgwater in the interest of the 4th Earl Poulett. The Earl of Egmont had funded his son Viscount Perceval to contest the seat, but Langston and Poulett's brother Vere won by a comfortable margin.